The present invention relates to a method of synchronization or cylinder coordination to crankshaft position in a multi-cylinder internal combustion engine.
In a multi-cylinder internal combustion engine with a crankshaft and a cam shaft, in which a control device calculates when and how much fuel must be injected per cylinder, it must be guaranteed that the fuel is supplied to the individual cylinders at proper time points and in a proper quantity. In order to perform the computations in a correct way, the corresponding position of the cam shaft or the crankshaft of the internal combustion engine must be known, and it is therefore conventional to provide a crankshaft and a camshaft transmitter which determines the position. For this purpose the crankshaft and the camshaft is connected each with a disk which has a predetermined number of angular marks. The disk connected with the crankshaft has for example n-e (for example 60-2) angular marks, which also form the reference marks by a gap between two angular marks. The disk connected with the cam shaft also has an angular mark. Both transmitter disks are scanned by a suitable pickup which provides an output signal corresponding to the surface of the disk.
Since in a four-stroke internal combustion engine, two crankshaft revolutions are required for a working cycle, in the normal situation the cylinder coordination to the crankshaft signal is performed by means of the signal from the camshaft transmitter. When the camshaft transmitter is not available, a redundant synchronization or in other words a cylinder coordination to the crankshaft signal can be performed exclusively from the crankshaft signal. Since the crankshaft signal supplies the reference marks in each revolution, no complete cylinder coordination to the crankshaft angle is possible.
For performing such a coordination, a control system for an internal combustion engine regulation is proposed in the German document DE-os40 40 828. Here with the known reference marks in the crankshaft signal from the control device of the internal combustion engine, an injection is performed in one or for one cylinder of the internal combustion engine, from which it is assumed that during occurrence of the reference mark it is located in an upper dead point. Since in the control device moreover the rotary speed of the internal combustion engine is continuously determined by evaluation of a predeterminable signal length of the crankshaft signals, it can be determined whether a rotary speed increase is caused by the probe measurement. The rotary speed increase as a result performs the probe injection only when the injected fuel is ignited. By the ignition or the combustion process, a rotary speed acceleration is caused, whereby the control device determines that the cylinder in which the injection was performed is located in the upper dead point. Thereby no synchronization, or in other words the cylinder coordination to the crankshaft signal is performed.
Since the position of all cylinders relative to the crankshaft cylinder is known, it is proposed in the German reference DE-OS 4,040,828 to use a control system for an internal combustion engine, in which in the case when the injection does not lead to a rotary speed increase or a rotary speed acceleration, the injection must be performed in a false cylinder. Then a synchronization is performed, and the synchronization in this case is displaced simply by 360xc2x0 KW.
Accordingly, it is an object of the present invention to provide a method of synchronization of a multi-cylinder internal combustion engine which avoids the disadvantages of the prior art.
More particularly, it is an object of the present invention to provide a method of synchronization of a multi-cylinder internal combustion engine which, when compared with the known solutions is more reliable and prevents a false synchronization with a great safety.
In keeping with these objects and with others which will become apparent hereinafter, one feature of present invention resides, briefly stated, in a method of synchronization of a multi-cylinder internal combustion engine, in which after the recognition of the reference mark of the crankshaft signal, first a first probe injection is formed in one or for one cylinder which is presumably located in an upper dead point.
If after the probe injection, a rotary speed increase or a rotary speed acceleration is obtained, the synchronization is performed or in other words the cylinder coordination to the crankshaft signal. If no rotary speed increase or no rotary speed acceleration is performed, a further preliminary acceleration is displaced by 360xc2x0. Then a further probe injection for a cylinder is performed, which is presumably in an upper dead point. It is then again checked whether a rotary speed increase is obtained. If this is the case, the final synchronization is performed. If no rotary speed increase is recognized, it is assumed that no combustion is performed, and the method is repeated until the synchronization is found or a predeterminable permitted number of probe injections is obtained.
The inventive method guarantees that in the case in which an injection at a proper time point or at a proper crankshaft angle does not lead to an ignition or a combustion, no fault synchronization is released. Thereby the inventive method also at low temperatures at which a correct injection does not lead to ignition can be utilized. The probe injections can be released in a preferable manner not always for the same cylinder in order to prevent an excessive loading. Moreover, in an advantageous manner it is prevented that an excessive fuel quantity is supplied to a cylinder. The sequence of the probe injections must not start preferably with the same cylinder. It is advantageous when the redundant synchronization step starts at each new start with a new cylinder, and it has to be taken into consideration that in many cylinders the ignition capacity relative to other cylinders is reduced.
The inventive method can be used in an especially advantageous manner in an internal combustion engine with a crankshaft and a camshaft transmitter, when the camshaft transmitter failed with. With this method the cam shaft transmitter is completely removed, and the synchronization is performed basically by the utilization of the crankshaft signals and the results of the probe measurements.
The novel features which are considered as characteristic for the present invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.